Work clamp mechanism for sewing machines

ABSTRACT

A work holding clamp for a cyclic sewing machine in which the stitch forming instrumentalities are organized with the loop taker arranged above the work and the needle therebeneath. The loop taker supporting bracket arm can be raised and lowered and a spacing member is provided between the loop taker supporting bracket arm and the upper jaw of the work clamp to provide uniform spacing between the work and the loop taker during sewing despite work thickness variation. The work clamp is also pivoted to the machine frame and articulated with respect to the work feeding mechanism so that the entire work clamp may be swung up to provide access to the needle.

United States Patent 11 1 Tiille 1111 3,783,807 [451 Jan.8, 1974 WORKCLAMP MECHANISM FOR SEWING MACHINES Giinter Tiille, Wendelinusstr. 15,Bruchsal, Germany 22 Filed: Feb. 16,1973

21 Appl.No.:333,079

[76] Inventor:

[50] Foreign Ap'pTiEitiTSri P36351355" M May 6, l972 Germany ..P 2222294.2

[52 US. Cl. 112/76 [51 Im. Cl D05b 3/04 [58] Field of Search 112/76, 70,65, 77

[56] References Cited 7 g UNITED STATES PATENTS 1,030,998 7/1912 Greeneetal. 112/76 x Primary rxamzher irfrraimstanmare? A Att0rney-Marshall.l. Breen et al.

[ XIIS 'IRACT A work holding clamp for a cyclic sewing machine in whichthe stitch forming instrumentalities are organized with the loop takerarranged above the work and the needle therebeneath. The loop takersupporting bracket arm can be raised and lowered and a spacing member isprovided between the loop taker supporting bracket arm and the upper jawof the work clamp to provide uniform spacing between the work and theloop taker during sewing despite work thickness variation. The workclamp is also pivoted to the 1 machine frame and articulated withrespect to the work feeding mechanism so that the entire work clamp maybe swung up to provide access to the needie.

8 Claims, Drawing Figures PATENTED JAN 8197 SHEET 1 BF 3 l. WORK CLAMPMECHANISM FOR SEWING MACHINES BACKGROUND OF THE INVENTION It has beenproposed heretofore to invert a sewing machine so that the loop takerwill be arranged above the work and the needle disposed therebeneath.The present invention, which pertains to a group stitch or cyclicallyoperable sewing machine such as a buttonhole sewing machine in which thework is held and shifted relatively to the sewing machine stitch forminginstrumentalities by a work clamp, comprehends a novel arrangement inwhich the positions of the needle and loop taker are inverted but inwhich the work clamp is not. The upper jaw of the work clamp may beraised to accommodate work fabrics face up therein and the loop takerwill be arranged above the face of the work and the needle carriedtherebelow.

A number of advantages accrue from the arrangement of this invention.Raised or pearl lockstitches set above the face of the work, which aretraditional in buttonhole stitching, can be formed using a preponderanceof needle thread so that the bobbin in the loop taker need bereplenished less frequently. Greater proportionate use of needle thread,moreover, reduces thread breakage because each unit length of needlethread will be worn less by passage back and forth through the needleeye.

Certain problems arise, however, in providing a reversal of theconventional arrangement between the work clamp and the stitch forminginstrumentalities of a cyclically operated sewing machine.

One problem whicharises is that of maintaining a constant distance fromthe loop taker to the surface of the work fabric despite variations inwork thickness.

Maintenance of this relationship, which is essential to propercooperation of the stitch forming instrumentalities, is preserved inconventional sewing machine con- I SUMMARY OF THE INVENTION Thisinvention provides a work clamp for a buttonhole sewing machine in whichthe needle is arranged beneath the work and the loop taker is carriedabove the work in an arm which may be swung upwardly to provideclearance for removing and replacing work fabrics. The work clamp isorganized right side up, i.e. with opposed jaws including a worksupporting plate beneath the work and a work holding foot having an openspace for the buttonhole and arranged above the work. The problem ofmaintaining constant distance between the loop taker and the workdespite work thickness variation is solved by providing a spacingelement preferably including an anti-friction roller between t'heswinging loop taker carrying arm and the work holding foot of the workclamp together with'resilient means acting beneath the work supportingplate which can yield to accommodate varying thicknesses of workfabrics.

DESCRIPTION OF THE DRAWINGS A preferred form of this invention isillustrated in the drawings in which:

FIG. 1 represents a side elevational view partly in verticalcross-section of a sewing machine having this invention applied theretoshowing the bracket arm lowered and the work clamp closed,

FIG. 2 is a side elevational view of the bracket arm portion of thesewing machine of FIG. ll showing the bracket arm swung up and the workclamp open,

FIG. 3 is a top plan view of the lower jaw of the work clamp with theparts being cut away substantially along line 33 of FIG. 2

FIG. 4 is a vertical cross-sectional view of the lower jaw of the workclamp taken substantially along line 4-4 of FIG. 3,

FIG. 5 is a perspective view of the lower jaw of the work clamp viewedfrom the rear of the machine and with the work supportingplatedisassembled, and

FIG. 6 is a disassembled perspective view of the connection elementsbetween the work clamp and the work clamp shifting mechanism.

As shown in the drawings,'the sewing machine to which this invention isapplied comprises a stationary frame base portion 11 formed with ears 12with which a bracket arm frame portion 13 is-pivotally mounted on apivot pin 14. A needle bar 15 to which a thread carrying needle 16 isclamped in endwise reciprocable in a gate 17 carried in the stationaryframe base portion 1 l. The needle bar is reciprocated endwise by adrive link 18 from a crank pin 19 fast on a main drive shaft 20. A looptaker 21 journaled in the bracket arm 13 is driven in timed relationwiththe needle by an arm shaft 22in the bracket arm carrying a sprocket 23driven by a timing belt 24 from a sprocket 25 on the main drive shaft20.

As shown in FIG. 2, the bracket arm 13 may be swung up to elevate theloop taker 21 out of cooperative relation with the needle for exchangeof work fabrics therebetween or for servicing of parts of the machine.Any known means may be employed for effecting pivotal movement of thebracket arm open and closed and for instance, a construction may be usedsuch as disclosed in the co-pending which is incorporated herein byreference.

The needle and loop taker arrangement described above represents aninversion of the arrangement which is conventional in sewing machines.The sewing machine disclosed in the accompanying drawings and with whichthe present invention is concerned moreover, is a cyclic or group stitchsewing machine that is, a sewing machine organized to produce apredetermined stitch group during each cycle of operation such as atack,,a buttonhole, or the like. It is well-known in the art of cyclicor group stitching sewing machines to provide a work clamp such asis-indicated generally at 3 in the accompanying drawings for grippingand shifting a work fabric relatively to the stitch forminginstrumentalities so as to provide the predetermined stitch group in thework fabric.

As shown in the drawings and best illustrated in FIG. 5, the work clampis associated with and shiftably supported relatively to a base platewhich is pivotally mounted on a pivot pin 41 carried in the cars 12 ofthe stationary machine frame base 11. The base plate 40 is thusstationary and although it cannot move with the work clamp duringformation of stitches, the base plate may be swung up about the pivotpin 14 when the bracket arm 13 is raised between stitching cycles.

Referring to FIG. 5, the work clamp 30 includes a lower jaw formed witha guide slot 46 and an aperture 47 in which a split clamp 48 is securedby means of fastening screws 49 which pass through a flange 50 of thesplit clamp and are threaded into the lower jaw 45. By means of a clampscrew 51 the split clamp 48 may be secured to a guide stud 52 of whichthe head 53 is constrained in an undercut guide slot 54 in the baseplate 40. By means of the guide slot 54 and a guide roller 55 carried bythe base plate and engaging the guide slot 46 in the lowerjaw 45, thework clamp will be constrained to move at an inclination to the baseplate 40 as shown in FIG. 3. It is pointed out, however, that thisinvention is not limited to a work clamp movable at such an inclination,but may be applied equally well to a work clamp movable parallel to thesewing machine base.

A roller may be carried by the base plate 40 underlying the lower jaw ofthe work clamp to facilitate free movement thereof. A similar roller 61is provided on the base plate engageable beneath a work supporting tray62 secured by screws 63 on top of the work clamp lowerjaw 45. The tray62 is formed with an aperture 64 exposing an anvil 65 on the base plate40 which is formed with a needle aperture 66 and with an elongated slot67 to facilitate cutting of the work material after a buttonhole hasbeen stitched therein.

The lowerjaw 45 of the work clamp carries a bracket 70 formed withspaced upstanding posts 71 carrying a pivot pin 72 for the upper jaw 73of the work clamp. Preferably, the upper jaw includes an arched arm 74carrying at its free extremity a work engaging shoe 75 formed with anopening 76 large enough to encompass the largest buttonhole which can bestitched by the sewing machine. The arched arm 74 of the work clampupper jaw carries a track 77 extending parallel to the buttonholeopening 76 in the work engaging shoe. The arched arm 74 is also formedwith a lip 78 extending parallel to the track 77. The track 77 and lip78 serve, as will be described hereinbelow, to cooperate with means forraising and lowering the work clamp upper As shown in FIGS. 4 and 5, asliding plate 80 is interposed between the lower jaw 45 of the workclamp and the base plate 40. The sliding plate carries a roller 81engaged in a guide slot 82 in the base plate and also carries a block 83which is slidable in a guide slot 84 in the base plate. The block 83 andthe roller 81 guide the sliding plate 80 in movement lengthwise of thesewing machine frame base 11. An inclined slot 85 formed in the slidingplate 80 embraces a roller 86 journaled on the stud 52 which guides thework clamp. Because of the inclination of the slot 85, the work clampcan partake of movement at an angle to the direction of movement of theslide plate 80.

As best shown in FIGS. 1 and 4, the mechanism for shifting the workclamp is carried by the stationary base portion 11 of the sewing machineframe and includes an angle bracket 90 secured to a hollow threaded studshaft 91. Threads on the stud shaft engage threads formed on aninternally threaded sleeve 92 journaled in the sewing machine frame base11. By way of a sprocket 93 clamped to the sleeve and engaged by atiming belt 94 the sleeve 92 may be turned in either direction to shiftthe angle bracket 90 back and forth.

While any conventional means might be provided for influencing work feedmovements of the work, reference is made to to which reference may behad for a detailed description of the mechanism disclosed in FIG. 1 forselectively indexing the timing belt 94 in increments first in onedirection and then in the other to feed the work clamp back and forthalong the length of a buttonhole.

The connection between the work clamp and the angle bracket 90 providesa resilient coupling which can accommodate swinging movement of the baseplate 40 about the pivot pin 41 without disrupting the drivingconnection with the angle bracket 90 which cannot swing up. Theresilient coupling as illustrated in FIGS. 4 and 6 comprises a fingerpivoted on a pin 101 in the block 83 and accommodated in a clearanceseat 102 formed in a constraining block 103 slidable in a guide slot 104in the angle bracket 90. A rod 105 attached to the constraining block103 extends through the hollow stud shaft 91 and accommodates dishedspring washers 106 beyond the hollow stud shaft and against a nut 107for applying spring bias to force the block 83 tightly against the anglebracket 90 as shown in FIG. 4.

Referring to FIGS. 1 and 2, the cooperative relation between the sewingmachine frame portions 11 and 13 and the work clamp 30 will now bedescribed.

The minimum spacing between the loop taker 21 and the work engaging shoe75 of the work clamp upper jaw is maintained by a wheel 110 which isjournaled on a pivot pin 111 in a clevis 112 sustained beneath thebracket arm 13. The clevis 112 is maintained in a position interposedbetween the bracket arm and the work clamp by a slide rod 113 which isconstrained in a bore 114 in the bracket arm. An elongated slot 115which is formed in the bracket arm and opens on to the bore 114,accommodates a lateral pin 116 carried by the slide rod 113. The pin 116serves not only to prevent turning of the clevis 112, but provides astop limiting the distance which the clevis-may be lowered beneath thebracket arm as shown in FIG. 2. A guide rod 117 on the clevis 112constrains a light coil spring 118 within a blind bore 119 in thebracket arm so as to bias the clevis away from the bracket arm. Theperiphery of the wheel 110 engages a track 77 on the arched arm 74 ofthe work clamp upper jaw and when the bracket arm is lowered intoeffective position for sewing as shown in FIG. 1, the clevis 112 willabut the bottom surface 120 of the bracket arm to define with the wheel110 a predetermined minimum spacing between the loop taker and the workclamp upper jaw.

When the bracket arm is raised as shown in FIG. 2 a lateral finger 121on the clevis 112 which engages beneath the lip 78 on the arched arm 74of the work draws the upper jaw upwardly into open position of the workclamp when the lateral pin 116 of the slide rod 113 engages the lowerextremity of the elongate slot 115.

When the upper jaw of the work clamp is elevated as the bracket arm isswung up, the lower jaw 45 and the base plate 40 with which the lowerjaw is associated, may also be swung up if they are grasped and elevatedby the machine operator. Elevation of the lower jaw and base plate maybe desirable, for instance, to gain clearance for threading the needleeye or the like. The resilient coupling between the work clamp and thework clamp shifting mechanism will accommodate such upward movement ofthe base plate without damage to or interference between parts.

When the bracket arm 13 is lowered into sewing position of the looptaker, the upper jaw of the work clamp will be pressed downwardlyagainst the lower jaw and the base plate 30 will be urged downwardlyagainst and in opposition to a plunger 130 which is shiftably supportedagainst a heavy coil spring 131 in a guide tube 132 secured in thestationary bed portion 11 of the sewing machine frame. A guide stud 133threaded into the plunger 130 and passing through the coil spring andthrough a guide aperture 134 in the inside of the guide tube 132 aids inaligning the plunger in the guide tube and provides a stop preventingthe plunger from accidentally being moved upwardly out of the guidetube. A washer 135 secured beneath the plunger is formed with a lateraltongue 136 accommodated in a vertical slot 137 in the side of the guidetube to prevent rotation of the plunger relatively to the guide stud133.

Having set forth the nature of this invention, what is claimed hereinis:

l. A sewing machine including a stationary frame portion having a needlecarrying bar supported therein, a bracket arm frame portion having aloop taker supported therein, a pivotal connection between said frameportions for movement of the loop taker into and out of a cooperativesewing position with relation to said needle carrying bar, a workengaging member supported between said frame portions contiguous to saidloop taker, characterized in that spacing means is provided forestablishing a predetermined minimum distance between the work engagingmember and the loop taker when the loop taker is moved into cooperativesewing position, and means carried on said stationary frame portion iseffective when the loop taker occupies cooperative sewing position forurging work fabrics against said work engaging member.

2. A sewing machine as set forth in claim 1 characterized in that saidwork engaging member is carried by one jaw of a work clamp which isshiftably supported between the sewing machine frame portions.

3. A sewing machine as set forth in claim 2 characterized in that saidspacing means includes a roller carried by the bracket arm frame portionand with a track carried on the work clamp jaw and disposedsubstantially parallel to the path along which said work clamp isshiftably supported.

4. A sewing machine as set forth in claim 1 characterized in that thespacing means also includes constraining means for limiting the maximumdistance which can exist between said loop taker and said work engagingmember when said bracket arm is shifted out of sewing position.

5. A sewing machine as set forth in claim 4 character ized in that thespacing means includes a clevis carried by a support rod which is guidedin a transverse bore formed, in said bracket arm and in that saidconstraining means comprises a lateral projection formed on said clevisand engaging said work clamp jaw and a lateral projection on saidsupport rod and engaging said bracket arm.

6. A sewing machine as set forth in claim 2 characterized in that saidwork engaging member is formed with an opening larger than the stitchpattern produced by the sewing machine, in that the opposing jaws of thework clamp are shiftablysupported on a base plate pivotally connected tosaid sewing machine frame, and in that the work clamp jaws are pivotallyinterconnected on an axis which is shiftable relatively to the pivotalconnection between said base plate and said sewing machine.

7. A sewing machine as set forth in claim 6 characterized in that a workclamp shifting mechanism is carried by said stationary sewing machineframe portion is provided with a resilient coupling with said work clampto accommodate movements of said base plate about which said pivotalconnection with said sewing machine frame.

8. A sewing machine as set forth in claim 7 characterized in that saidresilient coupling between said work clamp shifting mechanism and saidwork clamp comprises interengaging abutment elements on said work clampshifting mechanism and on said work clamp providing for a positivedriving connection therebetween in one direction of work clamp movement,and in that spring means is arranged in compression resilientlymaintaining said abutment elements in engagement during work clampmovements in the opposite direction.

1. A sewing machine including a stationary frame portion having a needlecarrying bar supported therein, a bracket arm frame portion having aloop taker supported therein, a pivotal connection between said frameportions for movement of the loop taker into and out of a cooperativesewing position with relation to said needle carrying bar, a workengaging member supported between said frame portions contiguous to saidloop taker, characterized in that spacing means is provided forestablishing a predetermined minimum distance between the work engagingmember and the loop taker when the loop taker is moved into cooperativesewing position, and means carried on said stationary frame portion iseffective when the loop taker occupies cooperative sewing position forurging work fabrics against said work engaging member.
 2. A sewingmachine as set forth in claim 1 characterized in that said work engagingmember is carried by one jaw of a work clamp which is shiftablysupported between the sewing machine frame portions.
 3. A sewing machineas set forth in claim 2 characterized in that said spacing meansincludes a roller carried by the bracket arm frame portion and with atrack carried on the work clamp jaw and disposed substantially parallelto the path along which said work clamp is shiftably supported.
 4. Asewing machine as set forth in claim 1 characterized in that the spacingmeans also includes constraining means for limiting the maximum distancewhich can exist between said loop taker and said work engaging memberwhen said bracket arm is shifted out of sewing position.
 5. A sewingmachine as set forth in claim 4 characterized in that the spacing meansincludes a clevis carried by a support rod which is guided in atransverse bore formed in said bracket arm and in that said constrainingmeans comprises a lateral projection formed on said clevis and engagingsaid work clamp jaw and a lateral projection on said support rod andengaging said bracket arm.
 6. A sewing machine as set forth in claim 2characterized in that said work engaging member is formed with anopening larger than the stitch pattern produced by the sewing machine,in that the opposing jaws of the work clamp are shiftably supported on abase plate pivotally connected to said sewing machine frame, and in thatthe work clamp jaws are pivotally interconnected on an axis which isshiftable relatively to the pivotal connection between said base plateand said sewing machine.
 7. A sewing machine as set forth in claim 6characterized in that a work clamp shifting mechanism is carried by saidstationary sewing machine frame portion is provided with a resilientcoupling with said work clamp to accommodate movements of said baseplate about which said pivotal connection with said sewing machineframe.
 8. A sewing machine as set forth in claim 7 characterized in thatsaid resilient coupling between said work clamp shifting mechanism andsaid work clamp comprises interengaging abutment elements on said workclamp shifting mechanism and on said work clamp providing for a positivedriving connection therebetween in one direction of work clamp movement,and in that spring means is arranged in compression resilientlymaintaining said abutment elements in engagement during work clampmovements in the opposite direction.